Time division duplex (TDD) wireless communication system realizes bi-directional communication with time-dividing same frequency and splitting one time frame into transmission (TX) and reception (RX) parts through certain timing sequence. The radio production test for the TDD radio units involves calibrating the characteristic and verifying the performance of the radio unit before leaving factory, including adjusting the transmitter/receiver chain gain in the radio unit when transmitting and receiving, and the like. A typical such radio production test system is depicted in FIG. 1. As illustrated, multiple TDD radio units (e.g. TDD radio units 1-3) are tested by the respective test stations (e.g. Test station 1-3) simultaneously in an independent manner. Usually, the physical locations of TDD radio units are close to each other. Hence, due to the use of the same TX/RX frequency, the electromagnetic wave interference among the radio units with the execution of the test cases by the different test stations is so evident that it deteriorates the accuracy of the production test. For example, when one TDD radio unit is running a TX test case, i.e. the TDD radio unit transmits specific signal to its corresponding test station (e.g. from TDD radio unit 1 to Test station 1), its radiated high power level electromagnetic wave can impact or block the normal same frequency RX test case running on another TDD radio unit, i.e. the another TDD radio unit receives a specific signal from its corresponding test station (e.g. from Test station 2 to TDD radio unit 2). In this case, radio unit 2 may receive the signal transmitted from the radio unit 1 except for the test station 2 unexpectedly, which may cause the RX test case for radio unit 2 to be distorted or blocked. In particular, it can cause false yield loss reported by the test station 2 or wrong RX calibrated data stored in the TDD radio unit 2, which could impact RX performance of radio unit 2 potentially after on-site.
The known solutions to the issue include: i) adding additional electromagnetic shielding boxes on each TDD radio unit to decrease radiated electromagnetic wave; ii) keeping long physical space among the TDD radio units. However their respective disadvantages are also obvious. For solution i), the additional hardware resources are needed in order to build shielding box, and the shielding quality of shielding box is difficult to be evaluated and guaranteed by supplier, thus the interference can not avoided thoroughly. For solution ii), the improvement is restricted by the space occupied by production line. Normally, the larger space may cause the waste of production resource.